The long-term objective of this research project is to gain an understanding of how gene expression is controlled at the molecular level. Frog virus 3 (FV3) replication in eukaryotic cells is used as a model system in meeting this objective. A physical, genetic and transcriptional map of the FV3 genome will be obtained utilizing the combined techniques of restriction endonuclease digestion and electron microscopy of DNA molecules. Marker rescue of ts mutants will be used to construct a genetic map. Transcriptional mapping will utilize molecular hybridization of individual FV3 mRNA species to restrictive endonuclease fragments. Structural proteins of FV3 will be isolated and characterized. Efforts will be made to identify biological functions of purified virion-associated proteins such as enzyme activities, switch-off and nongenetic reactivation. We will also investigate the mechanism of translational control of host cell protein synthesis by FV3 switch-off protein(s), and the mechanisms of translational control of viral protein synthesis by viral proteins. We will attempt to regulate the translation of virus -specific mRNAs in vitro; ts mutants with altered translational control will be utilized extensively in this portion of the research. Mechanisms of transcriptional control in FV3-infected cells will be analyzed. Methods to be used include standard virological, biochemical and molecular biological ones and include molecular hybridization, gel electrophoresis, peptide mapping and cell-free systems of protein synthesis.